If you want to figure out what is he the frequency of the your processor/processors and various other information related to the frequency of your system's processor, from the command line then the command cpufreq-info will come in handy.
cpufreq-info displays the frequency at which the various processors in the system are running at and also what is the possible range of frequencies for the processor.
For eg :
The other set of commands related to cpu frequency are
cpufreq-set : Which allows to modify the frequency settings for eg: the maximum frequency or the minimum frequency etc.
cpufreq-selector: This command allows you to set the frequency to one of the available values for the processor.
Have fun playing with the frequencies :-)